This invention pertains to providing nutritive supplements to mammals, in particular ruminants such as cattle.
Selenium, a nonmetallic element obtainable as a byproduct in copper refining, is a required nutrient for animals. While plants do not require selenium, they will take up soluble selenates if they are present. Herbivores generally receive the required amount of nutrient selenium if there is adequate selenium in the soils where the forage plants are grown.
However, there are areas where selenium is deficient in the soil. For example, selenium is deficient in soils of California north of Colusa, most of Oregon, Washington, and southwestern Canada. There are also large areas of selenium deficiency in the northeastern United States as well as other parts of the world.
Animals, particularly ruminants, feeding in these areas frequently develop acute selenium deficiency. Acute selenium deficiency results in fetal abortion, stillbirths, and "white muscle disease" in which muscle tissues fail to develop normally. Currently, the economic loss of domestic animals in California alone from selenium deficiency is about five million dollars per year.
The present method for combating selenium deficiency in domestic animals is by veterinary therapeutic injections. It may seem an easier and more economical method to apply selenium to pasture lands and the like and thus make up for the lack of selenium in the soil, but this has not proven possible. One major reason for this is that selenates (SeO.sub.4 -2) are very toxic to man and animal and thus dangerous to handle. Moreover, the range between the minimum required level of selenium in the diet (.about.40 ppb) and the toxic level (approximately 20 ppm) is very narrow, and because selenates are water-soluble, two problems arise. First, if applied to the soil in amounts which are nontoxic and beneficial to cattle, the solubility of the selenates is such that any significant irrigation or rainfall will leach the selenates from the applied soil, thus leaving the soil once again in a selenium-deficient condition. On the other hand, if the selenates are applied in large amounts to ensure sufficient selenates in the soil despite rainfall, the toxicity factor becomes of concern. Specifically, if the cattle were to ingest an overdose of selenium, blindness and/or brain damage, and even death, may result.